Control shaft



Nov. 18; 1941. H. w. RUBINSTEIN 2,263,399

CONTROL SHAFT Filed Jung 14, 1940 INVENTOR #9225 14 PUB/M5776! BY w ,W

' ATTORNEY Patented Nov. 18, 1941 CONTROL SHAFT Harry W. Rubinstein, Milwaukee, Wis., assignor to Globe-Union Inc., Milwaukee, Wis., a corporation of Delaware Application June 14, 1940, Serial No. 340,426

1 Claim.

This invention relates to an improvement in control shafts especially designed and adapted for use with electrical control devices of the type employed on radio sets, such, for example, as volume controls, tone controls, variable condensers, adjustable rheostats, switches, and the like.

A control shaft of this character is usually actuated or adjusted by means of a manually rotatable control knob mounted on and rotatively coupled to the outer end of the shaft. To adapt the shaft for this interconnection and rotative coupling with the control knob, it has been the practice in the art to flatten the outer end portion of the shaft. Because different styles of knobs require different degrees of flattening, it has been diflicult to standardize the manufacture of control shafts and avoid laborious and expensive modification thereof when assembling. This has led to the expedient of combining removable inserts with a specially constructed ridged shaft, as proposed in Patent No. 2,197,140, granted April 16, 1940, to M. J. Arvin, for a Control shaft.

The object of the present invention is to provide a control shaft which avoids the use of any inserts or extra parts. When constructed in accordance with the present invention, the control shaft is an integral article of manufacture and yet may be conveniently and effectively utilized with the various types of knobs.

In carrying out the present invention at least the end portion of the shaft is flattened and is characterized by the provision of a plurality of ribs separated by a plurality of narrow grooves. The ribs have flat top surfaces located in the same plane to present a flat on the shaft of substantial area to adapt it to be effectively interfitted with a large sized socket of a control knob. The grooves between the ribs are of uniform, predetermined depth and have fiat floors lying in the same plane. As the ribs are constituted of material readily filed away, or readily removable in any other appropriate fashion, the shaft may be easily converted for use with a small sized socket of a control knob merely by filing the ribs down to the level of the floors of the grooves.

Other objects and advantages reside in certain novel features of the construction, arrangement, and combination of parts, which will be hereinafter more fully described and particularly pointed out in the appended claims, reference being had to the accompanying drawing forming a part of this specification, and in which:

Figure 1 is a view in side elevation showing an electrical control device equipped with a control shaft embodying the present invention.

Figure 2 is a view in transverse cross section taken on line 2-2 of Figure 1 and showing the ribs still in place on the shaft.

Figure 3 is a view similar to Figure 2 but illustrating the construction of the shaft after the ribs have been removed or filed away.

Figure 4 is a fragmentary view partly in side elevation and partly in longitudinal, vertical cross section, showing how a control knob is combined with the outer end of the shaft with the ribs thereon.

Figure 5 is a view similar to Figure 4 but illustrating the control knob combined with the shaft after the ribs have been filed away.

Referring to the drawing, the numeral I0 designates an electrical control device, such as a volume control, or any other similar type of control. The device is regulated in its action by means of a control shaft II which is supported for rotation in the bushing I2 of the volume control in the usual way.

Beyond the bushing I2 the shaft is flattened, and the flattened portion is formed with a plurality of parallel, longitudinally extending ribs I3 separated by grooves I4. In the preferred embodiment of the invention at least three such ribs are provided. The ribs have fiat top surfaces which lie in the same plane so that the top surfaces present a flat of substantial area adapted to be effectively interfitted with the socket of a control knob I5, in the manner illustrated in Figure 4. The grooves I4 are of uniform, predetermined depth and have flat floors I5 lying in the same plane. The shaft is usually constructed of suitably soft metal, such as aluminum alloy, or the like, so that the ribs I3 may be readily filed or cut away down to the vlevel of the floors I5 of the grooves I4. This produces a shaft with a flat adapted to be combined with a knob I'I having a small sized socket therein in the manner illustrated in Figure 5.

In Figures 4 and 5 the outer ends of the shaft II ar merely shown as frictionally interfitted with the sockets of their control knobs. Of

course, various well-known types of fastening devices may also be employed to effect the desired interconnection between the sockets of the knobs and the outer ends of the shaft. Then, again, in Figures 2 and 3 it is indicated how the dimensions of the shaft are varied by filing away the ribs. Of course, the present invention is not limited to any particular dimensions.

While I have shown and described one conof provided with a flat face disposed in a plane substantially parallel to the axis of said shaft, the fiat face of said shaft being provided with a plurality of slots extending longitudinally of the shaft and penetrating said flat face to a substantially uniform depth, the several slots each terminating in a fiat floor, the several slot floors being separated by upstanding ribs, all of said floors being disposed in a common plane substantially parallel to the plane of said flat face, the said fiat face being dimensioned to properly fit within the shaft receiving socket of a knob having a large socket and the flat face collectively defined by the floors of said slots when the ribs are removed being dimensioned to properly fit Within the shaft receiving socket of a knob having a small socket.

HARRY W. RUBINSTEIN. 

